> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Thermal Analysis – Simulation Types

The quality or 'correctness' of the results of a simulation depends on its assumptions.

To enable the development of representative models, a brief overview of the different considerations relevant to a thermal analysis is presented below.

## Linear vs. Nonlinear Analysis

A nonlinear thermal problem, as opposed to a linear one, typically involves:

* Temperature-dependent material properties
* Temperature-dependent boundary conditions

## Thermal vs. Thermal Stress Analysis

A ***Thermal Analysis*** solves a thermal problem with only thermal quantities as results like temperatures and heat fluxes.

A ***Thermal Stress Analysis*** (also called ***thermo-elastic analysis***) solves for the mechanical behavior of a model in terms of stress, strain, deformation, etc. induced due to thermal loads, in addition to calculating the response due to other mechanical loads and boundary conditions.

→ Therefore, a thermal stress analysis is essentially a static structural analysis.

An additional thermal property, the ***coefficient of thermal expansion*** of the material, must be defined. The coefficient of thermal expansion (*SI units: 1/K*) describes how the size of an object changes with a change in temperature.

<Note>
  **Note**: The thermal stress analysis capability in nTop is uncoupled, i.e., only mechanical effects driven by thermal loads are calculated and not vice versa.
</Note>

## Steady-State vs. Transient Thermal Analysis

A ***steady-state thermal analysis*** calculates the thermal response at thermal equilibrium, with all thermal loads and boundary conditions in steady-state, with all effects of time essentially neglected. This type of analysis is analogous to solving a static structural FEA problem.

A ***transient thermal analysis***calculates a model's thermal response over a period of time. Thermal inertia effects due to density and specific heat of the material, therefore, become relevant. Solving a transient thermal analysis is analogous to solving a dynamic structural FEA problem.

<Tip>
  **Tip:** A steady-state thermal analysis applies when time behavior is irrelevant and only the results at equilibrium conditions are needed. A transient thermal analysis applies when thermal inertial effects are important or if there are extreme non-linearities in the model.
</Tip>